1. Field of the Invention
The invention relates to an optimizer for a parameter-dependent network system, comprising a plurality of controllers, which are interconnected by means of a network for communicating established input values and which generate control values for a controlled system. Control systems may include controllers whose input values come from the controlled system, so that a closed-loop control circuit is formed. It is, however, also possible that the input values do not come directly from the controlled system, so that an open-loop control system is produced.
2. Discussion of the Related Art
In the simplest case, the parameters of a controller can influence its amplification factors, or the like. For example, it is known to alter the parameters depending on the control output, i.e., based on the results of the control executed, a corrected controller is realized. Such a correction of the controller assumes a determined correlation between the parameter and the controller output. The correction of controllers reaches its limits whenever there is a more complex system in which the controllers are dependent on one another and/or influence one another. In this case, there are as a rule no determinable correlations between the controller output and the parameters. A correction of the parameters is not possible in this case. At best, one can only find suitable parameter combinations by trying them out in test runs of the control system. This is the case, as a rule, in a network.
If one considers, for example, a car as a control system, then it is evident that trying out parameters in test runs is sufficiently complex if the controllers of the engine, the transmission, and the brakes are designed with a communications network. It is, indeed, possible to simulate a network, which tests various parameter combinations, such as the size of the data bus used in the network as well as priority assignments for messages sent on the simulated system. However, this does not produce a reliable specification of an optimum parameter combination for the real system.
In the prior art, attempts have been made to design a network system equally optimal. There are "tools" on the market, which provide assistance in designing such a network system. These tools allow, in a first stage, a simulation of the sequence of communication and control operations in the network in accordance with boundary specifications of the system designer. This simulation is much slower than the real operation, but speed is not relevant to the application purpose. In a second stage, a partial simulation is made with an emulator in a network system which is partially of real design. An emulator of this type can be of realtime design. In the final stage, an analyzer checks the sequence of operations in the real network system assembled. Once the network is assembled, it is possible only with great difficulty to determine whether the parameters assigned to the individual controllers are optimal. For this it is necessary to carry out trials by a process which is hardly systematic. Rather, it can only be carried out in a random manner, due to the large number of possible parameter combinations.
Reference is made to applicant's co-pending application Ser. No. 213,951, filed Jul. 1, 1988, the contents of which are hereby incorporated in this application by reference, particularly with regard to a more detailed description of some of the components of the present invention.